5. Does it have to be LDAP? Can you make it a pluggable architecture w/
API so we can use whatever backend we want (MySQL/Postgres/SQLite, LDAP,
Active Directory, DT+BG server*, etc.)? This feature should be optional,
though. Centralized management of cluster configurations would be nice
but, as others have said, introduces possible dependencies and points of
failure.

cluster3 has exactly this feature implemented.

The issue is only for people to write plugins to load the configuration
from different sources.